Photovoltaic device

ABSTRACT

A photovoltaic device and a manufacturing method thereof are provided. The photovoltaic device includes: a substrate; a first conductive layer formed on the substrate; P layers and N layers alternately formed along a first direction on the first conductive layer; and I layers covering the P layers and the N layers on the first conductive layer, wherein the P layers and the N layers are separated from each other by a first interval, the I layers are formed between the P layers and the N layers that are separated by the first interval, and the P layers, the I layers, and the N layers formed along the first direction form unit cells.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application based on pending application Ser. No.12/486,654, filed Jun. 17, 2009, the entire contents of which is herebyincorporated by reference.

This application claims priority to and the benefit of Korean PatentApplication No. 10-2008-0104295 filed in the Korean IntellectualProperty Office on Oct. 23, 2008 and Korean Patent Application No.10-2008-0110615 filed in the Korean Intellectual Property Office on Nov.7, 2008, the entire contents of which are incorporated herein byreference.

BACKGROUND

1. Field

The present invention relates to a photovoltaic device and amanufacturing method thereof.

2. Description of the Related Art

A solar cell is one kind of photovoltaic device for converting lightenergy into electrical energy, and is used as a core element fordeveloping solar light. The solar cell is a diode consisting of a PNjunction, and may be classified into various kinds according to thematerial used as a light absorption layer.

A solar cell using silicon as the light absorption layer may beclassified as a crystalline (monocrystalline and polycrystalline) solarcell, a substrate solar cell, and a thin film (crystalline andamorphous) solar cell. Also, a representative solar cell may be acompound thin film solar cell using CIGS (CuInGaSe2) or CdTe, a III-Vgroup solar cell, a dye response solar cell, and an organic solar cell.

The thin film solar cell is formed by coating a film onto a substratebased on thin glass or plastic. With the common thin film solar cell,the diffusion distance of carriers is very short due to thecharacteristic of the thin film compared to that of the crystallinesilicon solar cells, and if it is fabricated only with the PN junctionstructure, the collection efficiency of electron-hole pairs generated bythe sunlight is significantly lowered. Therefore, the thin film solarcell has a PIN structure where an intrinsic semiconductor-based lightabsorbing layer with high light absorption is interposed between theP-type and N-type semiconductors. The common thin film solar cell has astructure where a front transparent conductive film, a PIN layer, and arear reflective electrode layer are sequentially deposited on asubstrate. In this structure, the light absorbing layer is depleted dueto the overlying P and underlying N layers with a high dopingconcentration so that an electric field is generated therein. As aresult, among the carriers generated in the light absorbing layer bysunlight, the electrons are collected at the N layer and the holes atthe P layer by way of drift of the internal electric field, therebygenerating an electric current.

However, when the PIN layer is formed in the vertical direction, severallaser patternings are executed to the cells when connecting theelectrodes of the P layer and the N layer of different cells such thatlayer damage may be generated and a remaining layer is generated on theside, thereby generating pattern deterioration. Accordingly theefficiency of the solar cell may be reduced.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

Accordingly, the present invention improves an interface characteristicof a solar cell, and increases photovoltaic efficiency thereof.

Also, the present invention improves photo-efficiency by connectingneighboring light absorption layers, suppresses the generation of alateral leakage current, and improves durability of connectionelectrodes formed on the light absorption layers.

A photovoltaic device according to an embodiment of the presentinvention includes: a substrate; a first conductive layer formed on thesubstrate; P layers and N layers alternately formed according to a firstdirection on the first conductive layer; and I layers covering the Players and the N layers on the first conductive layer, wherein the Players and the N layers are separated from each other by a firstinterval, the I layers are formed between the P layers and the N layersthat are separated by the first interval, and the P layers, the Ilayers, and the N layers formed according to the first direction formunit cells.

The first direction may be the same as a direction in which carriers aremoved.

The first interval may be in the range of 0.3 um to 2 um.

The unit cells formed according to the first direction may beelectrically connected to each other through the first conductive layer.

The unit cells formed according to the first direction may be separatedfrom each other by a second interval that is wider than the firstinterval.

A depletion layer formed between the unit cells separated by the secondinterval may be further included.

The unit cells formed on the substrate may be arranged into a pluralityof columns according to the first direction, and unit cells arranged inneighboring columns are separated by a third interval that is wider thanthe first interval.

The P layers and the N layers may include at least one of amorphoussilicon (a-Si), micro-crystalline silicon (mc-Si), and amorphous siliconcarbide (a-SiC).

The I layers may be made of amorphous silicon (a-Si) or amorphoussilicon germanium (a-SiGe).

The first conductive layer may be made of a transparent conductive layeror a reflective layer.

A second conductive layer formed on the I layers may be furtherincluded.

A manufacturing method of a photovoltaic device according to anotherembodiment of the present invention includes: forming a conductive layeron a substrate; alternately forming P layers and N layers according to afirst direction on the conductive layer; patterning the P layers and theN layers to be separated by a first interval; and forming I layerscovering the P layers and the N layers on the conductive layer andfilling between the P layers and the N layers to separate them.

The alternately forming of the P layers and the N layers may beperformed using a mask.

The patterning of the P layers and the N layers may be performed usinglaser scribing or wheel scribing.

The patterning of the P layers and the N layers may be performed usingchemical etching.

The patterning of the P layers and the N layers may include selectivelyetching a conductive layer along with the P layers and the N layers forthe P layers and the N layers to be separated by a first interval of 0.3um to 2 um.

The patterning of the P layers and the N layers may include forming unitcells separated from each other by a second interval that is wider thanthe first interval when defining the P layers and the N layers that areseparated by the first interval as unit cells.

The patterning of the P layers and the N layers may include arrangingthe unit cells in a plurality of columns according to the firstdirection on the substrate, and selectively etching the P layer, the Nlayer, and the conductive layer for the unit cells to be separated by athird interval that is wider than the first interval.

The alternately forming of the P layers and the N layers may furtherinclude forming a depletion layer between the unit cells that areseparated from each other when defining the P layers and the N layersthat are separated by the first interval as unit cells.

A photovoltaic device according to an embodiment of the presentinvention includes: a first cell including a lower first conductivelayer, a first light absorption layer, and an upper second conductivelayer sequentially deposited on a substrate; and a second cellneighboring the first cell and including a lower second conductivelayer, a second light absorption layer, and an upper first conductivelayer sequentially deposited on the substrate, wherein the first lightabsorption layer and the second light absorption layer are formed at thesame layer and are connected each other.

The lower first conductive layer of the first cell and the lower secondconductive layer of the second cell may be separated from each other,and a light absorption layer may be further included.

The upper second conductive layer of the first cell and the upper firstconductive layer of the second cell may be formed with the same layer asthe first and second light absorption layers, and may be electricallydisconnected each other.

A depletion region formed between the upper second conductive layer ofthe first cell and the upper first conductive layer of the second cellmay be further included.

An electrode portion formed between the upper second conductive layer ofthe first cell and the upper first conductive layer of the second cellmay be further included.

The electrode portion may include protrusions and depressions, and aflat portion, and the width of the flat portion may be substantiallyequal to or less than the width between the lower first conductive layerof the first cell and the lower second conductive layer of the secondcell.

The upper second conductive layer of the first cell and the upper firstconductive layer of the second cell may be formed with the same layer asthe first and second light absorption layers, and are separated fromeach other.

A non-conductive member formed between the upper second conductive layerof the first cell and the upper first conductive layer of the secondcell may be further included.

A first electrode formed between the substrate, and the lower firstconductive layer of the first cell and the lower second conductive layerof the second cell, may be further included.

A second electrode formed between the upper second conductive layer ofthe first cell and the upper first conductive layer of the second cell,and on a portion therebetween, may be further included.

The two neighboring cells may be connected by the first electrode whenthe first cell and the second cell connected by the second electrode area pair of cells.

The lower first conductive layer and the lower second conductive layermay be maintained between two neighboring pairs of cells.

A manufacturing method of a photovoltaic device according to anembodiment of the present invention includes: forming a lower firstconductive layer and a lower second conductive layer on a substrate;forming a light absorption layer on the lower first conductive layer andthe lower second conductive layer; forming an upper first conductivelayer and an upper second conductive layer on the light absorptionlayer; forming an upper electrode on the upper first conductive layerand the upper second conductive layer; and patterning the upperelectrode layer, the upper first conductive layer, the upper secondconductive layer, and the light absorption layer to form a first celland a second cell forming a pair of cells connected by the upperelectrode layer.

The method may further include forming a lower electrode on thesubstrate before forming the lower first conductive layer and the lowersecond conductive layer on the substrate.

The pair of cells including the first cell and the second cell may beconnected by the lower electrode.

The lower first conductive layer and the lower second conductive layermay be maintained between the pair of cells including the first cell andthe second cell.

The forming of the lower first conductive layer and the lower secondconductive layer on the substrate may include forming a firstsemiconductor layer on the substrate, respectively injecting a firstimpurity and a second impurity having an opposite polarity to that ofthe first impurity to two neighboring regions of the first semiconductorlayer by using a mask, and patterning the first semiconductor injectedwith the first impurity and the second impurity.

The forming of the lower first conductive layer and the lower secondconductive layer on the substrate may include selectively forming asemiconductor including the first impurity at the first region on thesubstrate and a semiconductor including the second impurity at thesecond region on the substrate by using a mask.

A depletion region may be formed between the upper first conductivelayer and the upper second conductive layer.

The method may further include removing a portion of the region betweenthe upper first conductive layer and the upper second conductive layer,and forming a non-conductive member before forming the upper firstconductive layer and the upper second conductive layer on the lightabsorption layer.

The forming of the upper first conductive layer and the upper secondconductive layer on the light absorption layer may include forming asecond semiconductor layer on the light absorption layer, andrespectively injecting a first impurity and a second impurity having anopposite polarity to that of the first impurity to two neighboringregions of the first semiconductor layer by using a mask. The forming ofthe upper first conductive layer and the upper second conductive layeron the light absorption layer may include selectively forming asemiconductor including the first impurity at the first region on thesubstrate and a semiconductor including the second impurity at thesecond region on the substrate by using a mask.

According to the present invention, the number of laser scribes may bereduced, thereby reducing the manufacturing cost of the solar cell andimproving the interface characteristic of the solar cell, and as aresult the efficiency of the photovoltaic device may be increased.

Also, light absorption layers between the neighboring cells areconnected thereby improving photo-efficiency, and the light absorptionlayers are filled in the separation spaces between the neighboring cellssuch that impurity adhesion or chemical contamination that may begenerated during the process is prevented, thereby suppressing a leakagecurrent of the side surface thereof. Also, the connection electrodebetween the cells is not floated on the light absorption layer, butcontacts the light absorption layer such that mechanical durability ofthe connection electrode may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a photovoltaic device according to anembodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II′ shown inFIG. 1.

FIG. 3 to FIG. 6 are cross-sectional views showing a manufacturingmethod of a photovoltaic device according to an embodiment of thepresent invention.

FIG. 7 is a cross-sectional view o a photovoltaic device according toanother embodiment of the present invention.

FIG. 8 and FIG. 9 are top plan views showing a structure forming anelectrode in a photovoltaic device according to an embodiment of thepresent invention.

FIG. 10 is a cross-sectional view for explaining a photovoltaic devicefor a solar cell according to another embodiment of the presentinvention.

FIG. 11 is a cross-sectional view for explaining a photovoltaic devicefor a solar cell according to another embodiment of the presentinvention.

FIG. 12 to FIG. 14 are cross-sectional views showing a manufacturingmethod of a photovoltaic device for a solar cell according to anotherembodiment of the present invention.

FIG. 15 and FIG. 16 are cross-sectional views for explaining aphotovoltaic device for a solar cell according to another embodiment ofthe present invention.

DETAILED DESCRIPTION

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. However, the present invention is not limited toembodiments described herein, and may be embodied in other forms.Rather, embodiments described herein are provided to thoroughly andcompletely understand the disclosed contents and to sufficientlytransfer the ideas of the present invention to a person of ordinaryskill in the art.

In the drawings, the thicknesses of layers and regions are exaggeratedfor clarity.

It is to be noted that when a layer is referred to as being “on” anotherlayer or substrate, it can be directly formed on the other layer orsubstrate or can be formed on the other layer or substrate with a thirdlayer interposed therebetween. Like constituent elements are denoted bylike reference numerals throughout the specification.

FIG. 1 is a top plan view of a solar cell according to an embodiment ofthe present invention. FIG. 2 is a cross-sectional view taken along theline II-II′ shown in FIG. 1.

Referring to FIG. 1 and FIG. 2, a transparent conductive layer 110 isformed on a substrate 100. An upper surface of the transparentconductive layer 110 is textured.

The texturing means that, for the purpose of increasing a valid lightamount absorbed to the inside of the solar cell by reducing light amountreflected from the solar cell surface, the upper surface of the firsttransparent conductive film 110 is formed with periodic pyramidalstructures, for example within a size of 10 μm by undergoing an etchingprocess.

The transparent conductive layer 110 may be made of SnO₂, ZnO:Al, ZnO:B,indium tin oxide (ITO), or indium zinc oxide (IZO) in one example.

P layers 120 a including impurities of a P type and N layers 120 bincluding impurities of an N type are alternately formed in a firstdirection D on the transparent conductive layer 110. The first directionD may be defined as a direction that the carriers are moved, that is,the direction that the electric field generated for the solar cell byabsorbing the light is moved.

The P layers 120 a may be made of one of boron-doped amorphous silicon(a-Si), amorphous silicon carbide (a-SiC), and microcrystalline silicon(mc-Si). The N layers 120 b may be made of one of phosphorus-dopedamorphous silicon (a-Si), amorphous silicon carbide (a-SiC), andmicrocrystalline silicon (mc-Si).

An I layer 130 covering the P layers 120 a and the N layers 120 b isformed on the transparent conductive layer 110. The I layer 130 is madeof an intrinsic semiconductor, functions as a light absorption layer,and generates an electric field to form a path through which the carrieris moved from the P layer 120 a to the N layer 120 b.

Each P layer 120 a and N layer 120 b are separated from each other witha first interval W1 therebetween, and the I layer 130 is formed in thefirst interval W1. Accordingly, in the solar cell according to anembodiment of the present invention, a P layer 120 a, the I layer 130,and an N layer 120 b form a unit cell UC in a lateral direction. In theunit cell UC, the upper surface and the side surfaces of the P layer 120a and the N layer 120 b are enclosed by the I layer 130. The I layer 130is made of amorphous silicon, thereby protecting the surfaces of the Player 120 a and the N layer 120 b, functions as an insulator therebypreventing a leakage current, and improves the interface characteristic,thereby improving the efficiency of the solar cell.

In one example, the first interval W1 is in the range of 0.3 um to 2 um.When the I layer 130 is formed of the amorphous silicon, if the firstinterval W1 is less than 0.3 um, the light conversion efficiency may bereduced by electron-hole recombination. When the I layer 130 is formedof the amorphous silicon, it is preferable that the first interval W1 isless than 2 um. However, when the degree of crystallization of the Ilayer 130 is improved to the degree of monocrystallinity, it is possiblefor the first interval W1 to be more than 2 um.

The unit cell UC is formed along the first direction D, the transparentconductive layer 110 is not formed between the P layer 120 a and the Nlayer 120 b in the unit cell UC, and the I layer 130 is filled therein.

The unit cells UC formed according to the first direction D areelectrically connected to each other through the transparent conductivelayer 110. In detail, the neighboring unit cells UC according to thefirst direction D have a second interval W2 therebetween. In the portionconnecting the neighboring unit cells UC, the transparent conductivelayer 110 formed under the P layer 120 a and the N layer 120 b is notdisconnected. The second interval W2 may be relatively wider than thefirst interval W1. In the connection portion of the unit cells UC thatare connected through the transparent conductive layer 110, the intervalW2 between the P layer 120 a and the N layer 120 b is relatively widerthan the interval W1 between the P layer 120 a and the N layer 120 b ineach unit cell UC such that the P layer 120 a and the N layer 120 b forma PIN diode through the I layer 130. In another embodiment, the P layer120 a and the N layer 120 b overlap each other and are doped on theportion connecting the neighboring unit cells UC, thereby being formedas a depletion layer. The depletion layer represents a non-conductivelayer.

In one example, the second interval W2 is in the range of 10 um to 100um.

The unit cells UC formed on the substrate 100 are disposed in aplurality of columns along the first direction D. The unit cells UCrespectively formed in neighboring columns are separated from each otherby a third interval W3. The third interval W3 is larger than theinterval W1 between the P layer 120 a and the N layer 120 b in the unitcell UC so as to not generate an interaction between the neighboringunit cells UC disposed in a direction intersecting the first directionD.

In one example, the third interval W3 may be in the range of 10 um to100 um.

A rear conductive layer 140 is formed on the I layer 130. The rearconductive layer 140 may be made of indium tin oxide (ITO) or indiumzinc oxide (IZO) in one example. The surface of the rear conductivelayer 140 is textured. The rear conductive layer 140 functions toincrease the light absorption rate by increasing a path through whichthe light is absorbed.

A reflective layer 150 is formed on the rear conductive layer 140. In anembodiment of the present invention, the rear conductive layer 140 andthe reflective layer 150 function as an electrode in the solar cell ofthe vertical type. However, the current flows in the sequence of thetransparent conductive layer 110, the P layer 120 a, the I layer 130,the N layer 120 b, and the transparent conductive layer 110 in thehorizontal direction such that the reflective layer 150 does notfunction as the electrode in an embodiment of the present invention, butfunctions to reflect the incident light through the substrate 100.

FIG. 3 to FIG. 6 are cross-sectional views showing a manufacturingmethod of a solar cell according to an embodiment of the presentinvention.

Referring to FIG. 3, a transparent conductive layer 110 is deposited ona substrate 100. The transparent conductive layer 110 may be made ofSnO₂, ZnO:Al, ZnO:B, indium tin oxide (ITO), or indium zinc oxide (IZO).The upper surface of the transparent conductive layer 110 is etched totexture the upper surface. P layers 120 a and N layers 120 b arealternately formed according to a first direction D on the transparentconductive layer 110. Next, various methods of alternately forming the Player 120 a and the N layer 120 b will be described in detail.

First, to alternately form the P layer 120 a and the N layer 120 b,first regions and second regions that are alternately disposed accordingto the first direction D are defined on the transparent conductive layer110. Next, the P layers 120 a are deposited in the first regions aftercovering the second regions by using a mask. In one example, the Players 120 a may be deposited through plasma enhanced chemical vapordeposition (PECVD). Next, the N layers 120 b are deposited in the secondregions after covering the first regions by using a mask. The N layers120 b may also be deposited through plasma enhanced chemical vapordeposition (PECVD).

In another method, an amorphous silicon layer is firstly formed on thetransparent conductive layer 110, and P-type ions are injected on thewhole surface of the amorphous silicon layer. Next, a portion where theP layers 120 a will be formed is covered and a portion where the Nlayers 120 b will be formed is exposed by using a mask, and an N-typeimpurity is injected with a high concentration and thereby the P layers120 a and the N layers 120 b are alternately formed.

In another method, an amorphous silicon layer is first formed on thetransparent conductive layer 110, a portion where the N layers 120 bwill be formed is covered and a portion where the P layers 120 a will beformed is exposed by using a mask, and the P-type impurity is injectedto form the P layers 120 a. Next, the portion where the P layers 120 awill be formed is covered and the portion where the N layers 120 b willbe formed is exposed by using a mask, and the N-type impurity isinjected to form the N layers 120 b.

In another method, an amorphous silicon layer doped with the P-typeimpurity is deposited on the transparent conductive layer 110 throughplasma enhanced chemical vapor deposition (PECVD). Next, a mask isdisposed on the amorphous silicon layer doped with the P-type impurityto cover the portion where the P layers 120 a will be formed, and N-typeions are injected to form the N layers 120 b. The layer of the P type ischanged to the I layer according to the injection of the N-type ions,and is then changed to the N-type layer. Accordingly, the P layers 120 aand the N layers 120 b may be alternately formed according to the firstdirection D.

FIG. 4 is a cross-sectional view explaining a method for alternatelyforming the P layers 120 a and the N layers 120 b according to anotherembodiment.

Referring to FIG. 1 and FIG. 4, depletion layers d between the unitcells UC are formed with the second interval W2. When forming the Players 120 a and the N layers 120 b by using the plasma enhancedchemical vapor deposition (PECVD) or the ion injection method, the Players 120 a and the N layers 120 b may be formed to overlap each otherin the portion where the unit cells UC1 and the unit cells UC2 areconnected to each other. If the portion where the unit cells UC areconnected is formed as an electrically non-conductive depletion layer,it is not necessary for the portion connecting the unit cells UC to besubsequently removed by using laser scribing.

Next, as shown in FIG. 5, the P layers 120 a and the N layers 120 b arepatterned to separate the P layers 120 a and N layers 120 b neighboringeach other by a predetermined interval. Patterning the P layers 120 aand the N layers 120 b is a process of connecting the electrodes whileforming the unit cells UC. In one example, the region where the P layer120 a and the N layer 120 b neighbor each other may be patterned bylaser scribing, wheel scribing, or chemical etching.

In the unit cell UC, the P layer 120 a and the N layer 120 b arepatterned to have the interval W1. The first interval W1 is formed to bein the range of 0.3 um to 2 um. The unit cells UC formed according tothe first direction D are patterned for the interval therebetween to bethe second interval W2. The second interval W2 may be wider than thefirst interval W1. The second interval W2 may be in the range of 10 umto 100 um.

The transparent conductive layer 110 may be selectively patterned at thesame time as the P layer 120 a and the N layer 120 b. In detail, asshown in FIG. 5, in the case of the portion where the unit cell UC1 andthe unit cell UC2 are connected, the transparent conductive layer 110 isleft as it is, and the regions neighboring the P layer 120 a and the Nlayer 120 b in each unit cell UC are selectively patterned. Accordingly,the unit cells UC1 and UC2 are electrically connected to each otherthrough the transparent conductive layer 110. In the regions consistingof the unit cells UC1 and UC2, the transparent conductive layer 110 issimultaneously patterned along with the P layer 120 a and the N layer120 b. When using laser scribing, the wavelength and the output of thelaser are controlled for etching, and an appropriate etchant is selectedwhen using the chemical etching process, so it is thereby possible toexecute the above-explained patterning.

The unit cells UC formed on the substrate 100 are disposed along thefirst direction D with the plurality of columns. The unit cells UC arepatterned to have the third interval W3 between the unit cells UC formedin neighboring columns. The third interval W3 is relatively wider thanthe first interval W1 so as to not generate an interaction betweenneighboring unit cells UC. The third interval W3 may be in the range of10 um to 100 um.

Referring to FIG. 6, an I layer 130 covering the P layer 120 a and the Nlayer 120 b is deposited on the transparent conductive layer 110. The Ilayer 130 may be made of amorphous silicon. The I layer 130 may beformed through plasma enhanced chemical vapor deposition (PECVD).

The deposited I layer 130 functions as a light absorption layer, and theP layer 120 a, the I layer 130, and the N layer 120 b are connected toform a diode according to the side direction.

A rear conductive layer 140 is formed on the I layer 130. The uppersurface of the rear conductive layer 140 may be etched, thereby forminga texture. The rear conductive layer 140 increases a path through whichthe light is absorbed, thereby increasing the light absorption rate.

A reflective layer 150 is deposited on the rear conductive layer 140 asshown in FIG. 2, thereby forming the solar cell shown in FIG. 1.

FIG. 7 is a cross-sectional view showing a solar cell according toanother embodiment of the present invention.

A solar cell of a substrate structure will now be explained. Light isincident through the substrate in the solar cell of the superstratestructure, however the light is incident on the side opposite to thesubstrate in the solar cell of the substrate structure. Hereafter,referring to FIG. 7, the solar cell of the substrate structure accordingto the current embodiment of the present invention will be described.

The solar cell of the substrate structure according to an embodiment ofthe present invention has the same planar shape as the solar cell of thesuperstrate according to an embodiment of the present invention, andFIG. 1 is again referred to. However, the reference numerals 100 of thesubstrate and 130 of the I layer of FIG. 1 are replaced with thereference numerals 200 for the substrate and the 230 for the I layer inthe solar cell of the superstrate structure according to the currentembodiment of the present invention.

Referring to FIG. 1 and FIG. 7, a reflecting electrode layer 210 isformed on a substrate 200. P layers 220 a including impurities of a Ptype and N layers 220 b including impurities of an N type arealternately formed along a first direction D on the reflecting electrodelayer 210. The first direction D may be defined as a direction in whichthe carriers are moved, that is, the direction that the electric fieldgenerated for the solar cell by absorbing the light is moved.

An I layer 230 covering the P layers 220 a and the N layers 220 b areformed on the reflecting electrode layer 210. The I layer 230 is made ofan intrinsic semiconductor, and is a path through which the carriers aremoved from the P layer 220 a to the N layer 220 b by generating theelectric field to the light absorption layer.

In the solar cell according to an embodiment of the present invention,the reflecting electrode layer 210 is used as the electrode of the Nlayer 220 b in the P layer 220 a, and simultaneously functions as thereflective layer. The reflecting electrode layer 210 may be made of ametal material.

The P layers 220 a including impurities of a P type and the N layers 220b including impurities of an N type are alternately formed along thefirst direction D on the reflecting electrode layer 210. The firstdirection D may be defined as a direction that the carriers are moved,that is, the direction that the electric field generated for the solarcell by absorbing the light is moved.

An I layer 230, covering the P layers 220 a and the N layers 220 b, isformed on the reflecting electrode layer 210. The I layer 230 is made ofan intrinsic semiconductor, and is a path through which the carriers aremoved from the P layer 220 a to the N layer 220 b by generating theelectric field to the light absorption layer.

Each P layer 220 a and N layer 220 b are separated by the first intervalW1 therebetween, and the I layer 230 is formed in the first interval W1.Accordingly, in the solar cell of the substrate structure according toan embodiment of the present invention, the P layer 220 a, the I layer230, and the N layer 220 b form unit cells UC along the side, like thesolar cell of the superstrate structure.

In the unit cells UC, the upper surface and the side surfaces of the Player 220 a and the N layer 220 b are enclosed by the I layer 230. The Ilayer 230 is made of an amorphous layer such that it functions as asurface passivation layer of the P layer 220 a and the N layer 220 b,prevents a leakage current, and improves the interface characteristic,thereby improving the efficiency of the solar cell.

The unit cells UC are formed along the first direction D, the reflectingelectrode layer 210 is not formed between the P layer 220 a and the Nlayer 220 b in the unit cell UC, and the I layer 230 is filled therein.

The unit cells UC formed according to the first direction D areelectrically connected to each other through the reflecting electrodelayer 210. In detail, the unit cells UC neighboring each other along thefirst direction D are separated by the second interval W2. In theportion connecting the neighboring unit cells UC, the reflectingelectrode layer 210 formed under the P layer 220 a and the N layer 220 bis not disconnected. The second interval W2 may be wider than the firstinterval W1. Accordingly, in the connection portion of the unit cells UCthat are connected by the reflecting electrode layer 210, the intervalW2 between the P layer 220 a and the N layer 220 b is wider than theinterval W1 between the P layer 220 a and the N layer 220 b in each unitcell UC such that the P layer 220 a and the N layer 220 b form a PINdiode through the I layer 230.

The unit cells UC formed on the substrate 200 are disposed in aplurality of columns according to the first direction D. The unit cellsUC respectively formed in neighboring columns are separated from eachother by a third interval W3. The third interval W3 is larger than theinterval W1 between the P layer 220 a and the N layer 220 b in the unitcell UC so as to not generate an interaction between the neighboringunit cells UC along the direction intersecting the first direction D.

A reflection prevention layer 250 is formed on the I layer 230. In thesolar cell of the superstrate structure, the light is incident on theopposite side of the substrate 200, and the reflection prevention layer250 protects the I layer 230 and does not reflect the incident lighttoward the I layer 230, and thus the reflection prevention layer 250 hasthe function of increasing the light absorption rate. In the solar cellof the superstrate structure according to an embodiment of the presentinvention, it is not necessary to additionally form the connectionelectrode on the reflection prevention layer 250 such that the problemthat the area receiving the light is decreased by the connectionelectrode is solved, thereby increasing the light absorption rate.

FIG. 8 and FIG. 9 are top plan views showing a structure forming anelectrode in a photovoltaic device according to an embodiment of thepresent invention.

Referring to FIG. 8 and FIG. 9, the unit cells UC are basicallyconnected in series with a zigzag shape. If all cells are connected inseries under a module formation, an efficiency deterioration may occurwhen generating dead cells or deteriorated cells, and the solar cell maynot operate in a serious case.

Accordingly, in the solar cell according to an embodiment of the presentinvention, connectors 300 and 400 connected to the edge of thetransparent conductive layer are connected in parallel to severalregions under the modulation process such that a short caused by deadcells and deteriorated cells, and consequent efficiency deterioration,may be prevented.

Also, the output voltage/current may be controlled according to themethod of forming the connectors 300 and 400.

According to embodiments of the present invention, it is possible forthe electrode and the unit cell to be formed through one patterningprocess such that interface defects and pattern deteriorations generatedthrough the patterning process may be solved.

FIG. 10 is a cross-sectional view for explaining a photovoltaic devicefor a solar cell according to another embodiment of the presentinvention.

Referring to FIG. 10, a front electrode 520 is formed on a substrate510. The substrate 510 is a hard substrate or a flexible substrate. Forexample, when the substrate is a hard substrate, it may include a glassplate, a quartz plate, a silicon plate, a plastic plate, or a metalplate. In another embodiment, when the substrate is a flexiblesubstrate, it may include a metal sheet or a plastic sheet. As anexample, the metal sheet may be a stainless sheet or aluminum foil.

The incident solar light is transmitted through the front electrode 520,which is made of a transparent conductive material having conductivity.Generally, the front electrode is made of a material that minimizes thedeterioration of light transmittance and that has low resistivity andgood surface roughness, such as a transparent conductive oxide (TCO)like ZnO:Al, ZnO:B, SnO2, and ITO. To increase the efficiency of theincident light, texture of a predetermined height and size may be formedon the surface of the front electrode 520, for example by etching.

A lower first conductive layer 531 and a lower second conductive layer532 having an opposite polarity to that of the lower first conductivelayer 531 and that neighbor each other are formed on the front electrode520. The lower first conductive layer 531 and the lower secondconductive layer 532 are separated from each other through a patterningprocess. A contact hole 534 exposing the substrate 510 by passingthrough the front electrode 520 is formed between the lower firstconductive layer 531 and the lower second conductive layer 532.

A light absorption layer 540 made of an intrinsic semiconductor materialis formed on the lower first conductive layer 531 and the lower secondconductive layer 532. Here, the light absorption layer 540 is connectedwith the substrate 510 through the contact hole 534, and separates thelower first conductive layer 531 and the lower second conductive layer532 from each other.

An upper second conductive layer 536 and an upper first conductive layer537 respectively corresponding to the lower first conductive layer 531and the lower second conductive layer 532 are formed at the same layeron the light absorption layer 540 to neighbor each other. A region wherethe upper second conductive layer 536 and the upper first conductivelayer 537 neighbor each other becomes a depletion region 535 bycombining the electrons and holes of the impurities that have thedifferent polarities and are injected to the upper second conductivelayer 536 and the upper first conductive layer 537, and isnon-conductive. It is possible for the depletion region 535 to bereplaced with an insulating member made of an organic material.

A rear electrode 550 is formed on the upper second conductive layer 536,the depletion region 535, and the upper first conductive layer 537. Therear electrode 550 includes protrusions and depressions 552 and a flatportion 551, and the width of the flat portion 551 corresponds to thewidth of the contact holes 534 such that it is substantially equal to orless than the width of the contact holes 534. The rear electrode 550 isgenerally made of a material such as silver (Ag), and a reflective layer(not shown) may be included between the upper second conductive layer536, the depletion region 535, and the upper first conductive layer 537,and the rear electrode 550.

When a first cell 571 and a second cell 572 connected through the rearelectrode 550 are referred to as a pair of cells, two neighboring pairsof cells are connected by the front electrode 520.

In this way, the first cell 571 made of the lower first conductive layer531, the light absorption layer 540, and the upper second conductivelayer 536, and the second cell 572 made of the lower second conductivelayer 532, the light absorption layer 540, and the upper firstconductive layer 537, are formed with the same layer such that a cellhaving the same effect as the vertical deposition structure such as intandem or triplet may be formed by being horizontally deposited.Particularly, the light absorption layer 540 is formed in the contacthole 534 between the lower first conductive layer 531 and the lowersecond conductive layer 532, and is connected on the boundary of thefirst cell 571 and the second cell 572 such that leakage current of thecell side generated by the adhesion of an impurity or chemicalcontamination may be reduced. Also, the light absorption layer formed onthe boundary between two neighboring cells functions as a supplyingsource of the carriers such that the lifetime of the minority carrier ofthe cell increases, thereby improving the light efficiency.

Also, the connection electrode between the neighboring cells is disposedon the depletion region 535 formed between the upper second conductivelayer 536 of the first cell 571, and the upper first conductive layer537 of the second cell 572 is not floated but is contacted with thelower layer, such that the mechanical durability may be improved.

FIG. 11 is a cross-sectional view for explaining a photovoltaic devicefor a solar cell according to another embodiment of the presentinvention.

Referring to FIG. 11, a rear electrode 620 is formed on a substrate 610.

The surface of the substrate 610 may include protrusions and depressionsto increase the reflection efficiency of solar light.

The rear electrode 620 is made of a metal having high reflectance, suchas Mo.

A lower first conductive layer 631 and a lower second conductive layer632 having an opposite polarity to that of the lower first conductivelayer 631 and that neighbor each other are formed on the rear electrode620. The lower first conductive layer 631 and the lower secondconductive layer 632 are separated from each other through a patterningprocess. A contact hole 634 exposing the substrate 610 by passingthrough the rear electrode 620 is formed between the lower firstconductive layer 631 and the lower second conductive layer 632.

A light absorption layer 640 made of an intrinsic semiconductor materialis formed on the lower first conductive layer 631 and the lower secondconductive layer 632. Here, the light absorption layer 640 is connectedwith the substrate 610 through the contact hole 634, and separates thelower first conductive layer 631 and the lower second conductive layer632 from each other.

An upper second conductive layer 636 and an upper first conductive layer637 respectively corresponding to the lower first conductive layer 631and the lower second conductive layer 632 are formed with the same layeron the light absorption layer 640 to neighbor each other. The regionwhere the upper second conductive layer 636 and the upper firstconductive layer 637 neighbor each other becomes a depletion region 635by combining the electrons and holes of impurities that have differentpolarities and are injected into the upper second conductive layer 636and the upper first conductive layer 637, and is non-conductive. It ispossible for the depletion region 635 to be replaced by an insulatingmember made of an organic material.

A front electrode 650 is formed on the upper second conductive layer636, the depletion region 635, and the upper first conductive layer 637.A reflection prevention layer (not shown) may be included between theupper second conductive layer 636, the depletion region 635, and theupper first conductive layer 637, and the front electrode 650. Thereflection prevention layer may be made of at least one material ofsilicon nitride, titanium oxide, and MgF2.

When a first cell 671 and a second cell 672 connected through the rearelectrode 650 are referred to as a pair of cells, two neighboring pairsof cells are connected by the rear electrode 620.

FIGS. 12 to 14 are cross-sectional views showing a manufacturing methodof a photovoltaic device for a solar cell according to anotherembodiment of the present invention.

FIG. 12 is a cross-sectional view showing a step of forming a frontelectrode 720 on a substrate 710.

Referring to FIG. 12, a front electrode layer 721 is formed on thesubstrate 710. As an example, the front electrode layer 721 is formedthrough physical vapor deposition. The front electrode layer 721 is madeof a material that is transparent and has conductivity, such as ZnO:Al,ZnO:B, SnO2, and indium tin oxide (ITO). To increase the efficiency ofincident light, it is preferable that the surface thereof is textured toa predetermined height and size. For example, the texture may include anembossing pattern, protrusions and depressions, protrusions, recesses,grooves, or a prism pattern.

The front electrode layer 721 is patterned to form the front electrode720. The patterning method may use laser scribing.

FIG. 13 is a cross-sectional view showing a step of forming a lowerfirst conductive layer 731 and a lower second conductive layer 732 onthe front electrode 720 formed by patterning the front electrode layer721 shown in FIG. 12.

Referring to FIG. 13, the lower first conductive layer 731 and the lowersecond conductive layer 732 are formed to neighbor each other on thefront electrode 720. Here, chemical vapor deposition may be used. Apredetermined region is exposed by using a hard mask (not shown), and athin film is deposited by using a deposition gas including a firstimpurity to thereby selectively form the lower first conductive layer731 on the predetermined region. Next, a region adjacent to the lowerfirst conductive layer 731 is exposed by using a hard mask, and a thinfilm is deposited by using a deposition gas including a second impurityhaving the opposite polarity to that of the first impurity, therebyselectively forming the lower second conductive layer 732 on the regionadjacent to the lower first conductive layer 731. A region 733 that isnot doped with an impurity may be present between the lower firstconductive layer 731 and the lower second conductive layer 732.

As another method of forming the lower first conductive layer 731 andthe lower second conductive layer 732, an intrinsic semiconductor layerthat does not include an impurity is formed on the front electrode 720,and impurities having different polarities are injected to theneighboring regions by using a hard mask.

As another method of forming the intrinsic semiconductor layer that doesnot include the impurity on the front electrode 720, a laser isirradiated to the semiconductor layer under a gas atmosphere includingan impurity such as PH3 or B2H6 such that the impurity in the gasatmosphere is reacted, thereby forming the lower first conductive layer731 and the lower second conductive layer 732.

After forming the lower first conductive layer 731 and the lower secondconductive layer 732, the boundary portion of the lower first conductivelayer 731 and the lower second conductive layer 732, and the lower frontelectrode 720, are removed by using laser scribing such that a pluralityof contact holes 734 exposing a portion of the substrate 710 are formed.The contact holes 734 may be formed in a ditch shape extending in onedirection under the plane surface. Here, the boundary portions of thelower first conductive layer 731 and the lower second conductive layer732 are removed while skipping one to form the conductive layer with thesame polarity on the right side and the left side with respect to thecontact holes 734.

FIG. 14 is a cross-sectional view showing formation of a lightabsorption layer 740, an upper second conductive layer 736, and an upperfirst conductive layer 737, as well as a rear electrode 750.

Referring to FIG. 14, the light absorption layer 740 is formed on thesubstrate 710 formed with the front electrode 720, the lower firstconductive layer 731, and the lower second conductive layer 732, and inthe contact holes 734, through chemical vapor deposition. Next, theupper second conductive layer 736 and the upper first conductive layer737 are formed on the light absorption layer 740. Here, the upper secondconductive layer 736 and the upper first conductive layer 737 havingopposite polarities are disposed at positions corresponding in thevertical direction to the lower first conductive layer 731 and the lowersecond conductive layer 732, respectively. The method of forming theupper conductive layers may be the same as the method of forming thelower conductive layers thereunder. Here, a depletion region 735 may beformed between the upper second conductive layer 736 and the upper firstconductive layer 737. In the depletion region 735, impurities having thedifferent polarities are injected such that combinations ofelectron-hole pairs are formed, and the charge carriers are depleted inthis region such that this region become a region that is electricallydisconnected. When the upper second conductive layer 736 and the upperfirst conductive layer 737 are formed through the impurity injectionusing a hard mask, the upper second conductive layer 736 and the upperfirst conductive layer 737 are formed to be separated from each othersuch that the intrinsic semiconductor region may be formed between theupper second conductive layer 736 and the upper first conductive layer737 to thereby obtain the same effects. Also, the depletion region 735may be eliminated, or may be replaced by an insulating member of aninorganic layer or organic layer.

A rear electrode 750 is formed on the substrate formed with the lightabsorption layer 740, the upper second conductive layer 736, the upperfirst conductive layer 737, and the depletion region 735. The materialfor the rear electrode 750 may be one of Ag, Mo, and Al.

Next, the rear electrode 750, the upper second conductive layer 736, theupper first conductive layer 737, the light absorption layer 740, thelower first conductive layer 731, and the lower second conductive layer732 are patterned through laser scribing or photolithography such that afirst cell 771 and a second cell 772 are connected by the rear electrode750 thereby forming a pair, and a structure in which pairs of a firstcell 771 and a second cell 772 are only connected by the front electrode720 is formed.

Accordingly, the first cell including the lower first conductive layer,the light absorption layer, and the upper second conductive layer, andthe second cell including the lower second conductive layer, the lightabsorption layer, and the upper first conductive layer are formed withthe same layer to neighbor each other such that a cell having the sameeffect as the vertical deposition structure such as tandem or tripletmay be formed by being horizontally deposited. Particularly, the lightabsorption layer is formed in the contact hole between the lower firstconductive layer and the lower second conductive layer, and is connectedon the boundary of the first cell and the second cell such that leakagecurrent of the cell side generated by adhesion of an impurity orchemical contamination may be reduced. Also, the light absorption layerformed on the boundary between two neighboring cells functions as asupplying source of the carrier such that the lifetime of the minoritycarrier of the cell increases, thereby improving the light efficiency.

FIG. 15 and FIG. 16 are cross-sectional views for explaining aphotovoltaic device for a solar cell according to another embodiment ofthe present invention.

In an embodiment of FIG. 15, compared with the embodiment of FIG. 10, adepletion region formed between the lower first conductive layer 531 andthe lower second conductive layer 532 is not removed, but is maintained,as well as the front electrode 520 between the cells in which the firstcell 571 and the second cell 572 are connected to each other by the rearelectrode 550. Thus, the portion that will be removed through the laserscribing is decreased such that thermal damage due to the laserirradiation may be reduced.

In an embodiment of FIG. 16, compared with the embodiment of FIG. 11, adepletion region formed between the lower first conductive layer 631 andthe lower second conductive layer 632 is not removed, but is maintained,as well as the rear electrode 620 between the cells in which the firstcell 671 and the second cell 672 are connected to each other by thefront electrode 650. Thus, the portion that will be removed through thelaser scribing is decreased such that thermal damage due to the laserirradiation may be reduced.

While this invention has been described in connection with what ispresently considered to be practical embodiments, it is to be understoodthat the invention is not limited to the disclosed embodiments, but, onthe contrary, is intended to cover various modifications and equivalentarrangements included within the spirit and scope of the appendedclaims.

1.-19. (canceled)
 20. A photovoltaic device, comprising: a first cellcomprising a lower first conductive layer, a first light absorptionlayer, and an upper second conductive layer sequentially deposited on asubstrate; and a second cell neighboring the first cell, and comprisinga lower second conductive layer, a second light absorption layer, and anupper first conductive layer sequentially deposited on the substrate,wherein the first light absorption layer and the second light absorptionlayer are formed at the same layer and are connected to each other. 21.The photovoltaic device of claim 20, wherein the lower first conductivelayer of the first cell and the lower second conductive layer of thesecond cell are separated from each other.
 22. The photovoltaic deviceof claim 21, wherein the upper second conductive layer of the first celland the upper first conductive layer of the second cell are formed withthe same layer as the first and second light absorption layer, and areelectrically disconnected from each other.
 23. The photovoltaic deviceof claim 22, further comprising a depletion region formed between theupper second conductive layer of the first cell and the upper firstconductive layer of the second cell.
 24. The photovoltaic device ofclaim 23, further comprising an electrode portion formed between theupper second conductive layer of the first cell and the upper firstconductive layer of the second cell.
 25. The photovoltaic device ofclaim 24, wherein the electrode portion comprises protrusions,depressions, and a flat portion, and the width of the flat portion issubstantially equal to or less than the width between the lower firstconductive layer of the first cell and the lower second conductive layerof the second cell.
 26. The photovoltaic device of claim 21, wherein theupper second conductive layer of the first cell and the upper firstconductive layer of the second cell are formed with the same layer asthe first and second light absorption layer, and are separated from eachother.
 27. The photovoltaic device of claim 26, further comprising anon-conductive member formed between the upper second conductive layerof the first cell and the upper first conductive layer of the secondcell.
 28. The photovoltaic device of claim 20, further comprising afirst electrode formed between the substrate, and the lower firstconductive layer of the first cell and the lower second conductive layerof the second cell.
 29. The photovoltaic device of claim 28, furthercomprising: a second electrode formed between the upper secondconductive layer of the first cell and the upper first conductive layerof the second cell, and on a portion therebetween.
 30. The photovoltaicdevice of claim 29, wherein the two neighboring cells are connected bythe first electrode when the first cell and the second cell connected bythe second electrode are a pair of cells.
 31. The photovoltaic device ofclaim 30, further comprising a depletion region formed with the samelayer as the lower first conductive layer and the lower secondconductive layer and formed between two neighboring pairs of cells.32.-41. (canceled)